Abstract
Myeloid cells are critical for innate immunity and the initiation of adaptive immunity. Strict regulation of the adhesive and migratory behavior is essential for proper functioning of these cells. Rho GTPases are important regulators of adhesion and migration; however, it is unknown which Rho GTPases are expressed in different myeloid cells. Here, we use a qPCR-based approach to investigate Rho GTPase expression in myeloid cells.We found that the mRNAs encoding Cdc42, RhoQ, Rac1, Rac2, RhoA and RhoC are the most abundant. In addition, RhoG, RhoB, RhoF and RhoV are expressed at low levels or only in specific cell types. More differentiated cells along the monocyte-lineage display lower levels of Cdc42 and RhoV, while RhoC mRNA is more abundant. In addition, the Rho GTPase expression profile changes during dendritic cell maturation with Rac1 being upregulated and Rac2 downregulated. Finally, GM-CSF stimulation, during macrophage and osteoclast differentiation, leads to high expression of Rac2, while M-CSF induces high levels of RhoA, showing that these cytokines induce a distinct pattern. Our data uncover cell type specific modulation of the Rho GTPase expression profile in hematopoietic stem cells and in more differentiated cells of the myeloid lineage.
Highlights
Within the immune system many different cell types carry out specific roles to ensure proper immunity, both innate as well as adaptive
GDPbound Rho GTPases are sequestered by Rho guanine nucleotide dissociation inhibitor (RhoGDI) [4], which serves as a molecular chaperone and regulator to protect the cell from aberrant GTPase activation
We isolated monocytes by adherence to plastic or by CD14+-Macs isolation and differentiated these further to macrophages, dendritic cells (DCs) and osteoclasts
Summary
Within the immune system many different cell types carry out specific roles to ensure proper immunity, both innate as well as adaptive. Cells of myeloid origin mediate innate immune responses but are essential for the initiation of adaptive immunity. The guanine nucleotide-exchange factors (GEFs) regulate the activation of Rho GTPases by promoting the exchange of GDP for GTP, while GTPaseactivating proteins (GAPs) promote the intrinsic GTPase activity and the transition back to the GDP-bound state [2,3]. GDPbound Rho GTPases are sequestered by Rho guanine nucleotide dissociation inhibitor (RhoGDI) [4], which serves as a molecular chaperone and regulator to protect the cell from aberrant GTPase activation. The balanced action of GEFs and GAPs is crucial for proper functioning of Rho GTPases and controls the timing and localization of Rho GTPase activity. Rho GTPases are regulated at the level of stability and expression
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